多组元BaO–SrO–CaO–MgO–Al2O3–2SiO2环境障涂层的制备与抗CaO–MgO–Al2O3–SiO2腐蚀性能

采用固相法制备不同摩尔 Ba、Sr、Ca、Mg 配比的 Ba O–Sr O–Ca O–Mg O–Al₂O₃–SiO₂ （BSCMAS）陶瓷材料,研究多组元陶瓷的制备工艺、显微结构及其抗 CMAS 腐蚀性能。结果表明：通过调控 MgO 的含量,在 1 400 ℃条件下制备了Ba_0.3Sr_0.3Ca_0.35Mg_0.05Al₂Si₂O₈ (B_0.3S_0.3C_0.35M_0.05AS)单相多组元陶瓷材料。在 1 250、1 300 ℃和 1 350 ℃对 B_0.3S_0.3C_0.35M_0.05AS 进行 CMAS 腐蚀实验,相比于 Ba_0.5Sr_0.5Al     

Optical properties of novel oxyfluoride glasses on the systems of LaF3–LaO3/2–NbO5/2 and LaF3–LaO3/2–NbO5/2–AlO3/2

Oxyfluoride glasses of xLaF₃–(60 − x)LaO_3/2–40NbO_5/2 (x = 0, 5, 10, 35) and xLaF₃–(60 − x)LaO_3/2–30NbO_5/2–10AlO_3/2 (x = 0, 10, 20, 30) were prepared using a levitation technique. Both the glass-transition temperature, T_g, and onset crystallization temperature, T_c, were lowered by substituting a part of the oxygen with fluorine in the glasses. An appropriate amount of fluorine maximized the difference between the temperatures, ΔT (= T_c − T_g), indicating the improvement in the glass-forming ability. The atomic packing densities of the glasses were approximately 60%, which gradually increased with the fluorine content. The absorption edge of the glasses shifted toward the shorter wavelength region in the ultraviolet spectra and toward the longer region in the infrared spectra by fluorine substitution. In addition, in one of the oxyfluoride glasses, a wide transparency from 307 nm to 9.2 µm was realized. Furthermore, the glass exhibited superior optical properties, with a combination of a high refractive index, n_d, of 2.020 and low wavelength dispersion, v_d, of 30.1. The effect of fluorine substitution on the n_d and its v_d was analyzed using the Lorentz–Lorenz dispersion formula.     

Fiber/matrix interfacial shear strength of C/C composites with PyC–TaC–PyC and PyC–SiC–TaC–PyC multi-interlayers

The fiber/matrix (F/M) interfacial shear strength (IFSS) of carbon/carbon (C/C) composites with PyC–TaC–PyC and PyC–SiC–TaC–PyC multi-interlayers was investigated. To obtain C/C composites with PyC–TaC–PyC and PyC–SiC–TaC–PyC multi-interlayers, a thin layer of PyC was deposited on carbon fibers. After this, TaC and SiC–TaC layer(s) were uniformly deposited on the PyC coated carbon fibers. As an outer-layer, a PyC layer was deposited on these TaC and/or SiC–TaC coated carbon fibers by isothermal chemical vapour infiltration (CVI) and then densified with resin carbon by impregnation and carbonization. Finally, C/C composites with PyC–TaC–PyC and PyC–SiC–TaC–PyC multi-interlayers were obtained. The effects of PyC–TaC–PyC and PyC–SiC–TaC–PyC multi-interlayers on interfacial shear strength (IFSS) of C/C composites were investigated. Single fiber push-out tests were conducted on the fibers aligned perpendicularly on the thin slices specimen surface using nano-indentation. Results showed that the IFSS of C/C composites decreased with the introduction of PyC–TaC–PyC and PyC–SiC–TaC–PyC multi-interlayers. After heat treatment (at temperatures ranging from 1400 to 2500 °C) of C/C composites with PyC–TaC–PyC multi-interlayers, it was found that the IFSS decreased with the increase in temperature. This decrease in IFSS is explained by taking into account the microstructural variations on heat treatment.     

Composite wasteform based on SiO2–PbO–CaO–ZrO2–TiO2–(B2O3–K2O) parent glass with zircon as the second component

Many different types of glass and ceramic wasteforms have been investigated for nuclear waste immobilization. This study deals with synthesizing composite wasteforms based on a parent glass belonging to the SiO₂–PbO–CaO–ZrO₂–TiO₂–(B₂O₃–K₂O) system with the use of zircon as a second component. The fabrication involves powder mixing, pressing and pressureless sintering. The processing conditions were investigated so as to achieve the highest density and the best sintering temperature for different amounts of zircon, i.e. 5, 10 and 15 wt%. The sintered products were studied by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM); as well as ICP-MAS for leaching experiments. The most promising composite containing zirkelite and titanite crystals in a lead-rich glassy matrix was obtained at 700 °C for 10 wt% zircon.     

Apatite and garnet stability in the Al–Ca–Mg–Si–(Gd/Y/Yb)–O systems and implications for T/EBC: CMAS reactions

This work advances the understanding of the influence of rare earth (RE) ion radius on the stability and extent of the garnet solid solution phase in the (ytterbia/yttria/gadolinia)-calcia-magnesia-alumina-silica systems. Guided by the crystal chemistry and charge neutrality constraints, selected compositions in the notional garnet stability field were synthesized, equilibrated at 1400°C, and characterized to determine the equilibrium phases and their compositions. The results show a significant reduction in the stability of the silicate garnet relative to apatite with increasing RE ion radius. Apatite was not observed for any composition in the Yb-containing system, the Y-containing system formed both garnet and apatite, and there was no evidence of silicate garnets in the Gd-containing system. However, despite the apparent differences in stability relative to apatite, the extent of the garnet solid solution increases only slightly for the Yb- compared to Y-containing systems. The quantitative microchemical analysis suggests that Mg²⁺ prefers the octahedral site over the dodecahedral site in the garnet structure, and that the solubility of Mg²⁺ in the dodecahedral site increased in the system containing Yb³⁺ compared to Y³⁺. The results are discussed for their relevance to reactions between RE-containing thermal and environmental barrier coatings and CMAS-type silicate deposits.     

Mechanosynthesis of nanocomposites in TiO2–B2O3–Mg–Al quaternary system

The mechanochemical behavior of TiO₂–B₂O₃–Mg–Al quaternary system to synthesize various composite nanopowders was studied. A mixture of boron oxide and titanium dioxide powders along with different amounts of magnesium and aluminum was milled using a high-energy planetary ball mill to persuade necessary conditions for the occurrence of a mechanically induced self-sustaining reaction (MSR). Results showed that the formation of composite nanopowders was influenced strongly by the reducing agents content. In the absence of Al (100 wt% Mg), TiB₂ nanopowder was formed after 34 min of milling. In the presence of x wt% Mg–y wt% Al (x=40 and 70; y=100−x), mechanical activation was completed after 37–40 min which caused the formation of TiB₂–MgFe_0.6Al_1.4O₄ composite nanopowders. In the case of 10 wt% Mg–90 wt% Al, a ternary nanocomposite (TiB₂–MgAl₂O₄–Al₂O₃) was produced after 43 min of milling. Besides, Al₂O₃–TiB₂ nanocomposite was formed after 90 min of milling in the absence of Mg (100 wt% Al). From the SEM images, mechanochemical process reached a steady state after short milling times where the particles have become homogenized in size and shape. The reaction mechanism steps were proposed to clarify the reactions occurring during mechanochemical process.     

Crystallization behavior and properties of K2O–CaO–Al2O3–SiO2 glass-ceramics

In order to obtain high-strength anorthite glass-ceramics, K₂O–CaO–Al₂O₃–SiO₂ quaternary glass and relevant glass-ceramics were prepared and investigated. The results show that anorthite along with kalsilite or leucite was precipitated from the parent glass. Kalsilite crystals were formed firstly and then converted into leucite through reacting with SiO₂ in the glass phase. The morphology of the crystals was dependent on the heat-treatment temperature. Column crystals were transformed into fine granular grains when the sintering temperature changed from 900 °C to 1100 °C. The activation energy (E_α) and avrami constant (n) were also calculated as 463.81 KJ/mol and 3.74 respectively, indicating that bulk nucleation and three-dimensional crystal growth were the dominating mechanisms in the temperature range 1000–1100 °C. The maximum value of the flexural strength for the glass-ceramics containing leucite was 248 MPa and the coefficient of thermal expansion (CTE) was in the range 5.69~11.94×10⁻⁶ K⁻¹. The leucite is the main reason for the high CTEs and high flexural strength of glass-ceramics.     

Bi2O3对K2O–B2O3–SrO–Al2O3–Nb2O5–SiO2玻璃陶瓷介电储能性能的影响

随着电力电子系统的不断发展,高功率脉冲电容器的需求增多。电介质电容器因具有放电功率大、充放电速度快及性能稳定等优点,在电力系统、电子器件、脉冲电源等方面发挥着重要作用,广泛应用于民用领域及军事领域。通过熔融压延制备玻璃基体,采用可控结晶工艺研究了不同含量的Bi₂O₃ (x=0.0%、1.0%、2.0%、4.0%,摩尔分数)对K₂O–B₂O₃–Sr O–Al₂O₃–Nb₂O₅–SiO₂玻璃陶瓷物相演化、微观结构、介电和储能性能的影响。在该玻璃陶瓷中,KSr₂Nb₅O₁₅为主要析出晶相,当Bi₂O₃的加入量为x=2.0%(摩尔分数)时,热处理温度为950℃时,玻璃陶瓷样品的储能密度最大可达到1.27 J/cm³,室温下介电常数可达342,是热处...     

Thermodynamic analysis on the codeposition of ZrC–SiC by chemical vapor deposition using the ZrCl4–C3H6–MTS–H2–Ar system

A thermodynamic calculation on co-deposition of ZrC–SiC from the ZrCl₄–C₃H₆–MTS–H₂–Ar system was performed using the FactSage thermochemical software and verification experiments were performed. The surface diagrams of condensed-phases in this system were expressed as functions of the deposition temperature, total pressure, reactant ratio of MTS/(MTS+C₃H₆) and ratio of H₂/(ZrCl₄+MTS+C₃H₆), and the composition of the products was determined by the diagram. The calculation results indicate that their yields strongly depend on the molar ratio of the injected reactants and temperature, and ZrC–SiC can be co-deposited under a proper condition. The experimental results show that ZrC–SiC coating was successfully co-deposited on graphite substrates and carbon fibers according to the thermodynamic calculation.     

The reaction between the magnesia–chrome brick and the molten slag of MgO–Al2O3–SiO2–CaO–FetO and the resulting microstructure

The reaction and microstructure at the interface of MgO–Cr₂O₃ brick and the molten slag of MgO–Al₂O₃–SiO₂–CaO–Fe_tO after static slag corrosion at 1823–1923 K for various times and the resulting microstructure were investigated and characterized. After the static slag corrosion at 1923 K for 4 h, the XRD results show the major phases of periclase MgO, MgCr₂O₄ spinel, and CaMgSiO₄ as the minor phase. MgCr₂O₄ phase causes MgO to form a discontinuous phase in MgO–Cr₂O₄ brick. After static slag corrosion at 1923 K for 4 h, SEM micrographs show that brick interior cracks, MgO and dissolved MgO. MgO dissolved due to the molten plag penetrated into the brick interior and reaction with it, leading to a localized dissolution of brick slag. TEM micrographs and ED patterns demonstrate that the minor phase of (Mg, Fe)(Al, Cr)₂O₄ precipitates in the MgCr₂O₄ matrix.     

Effects of PbO and SrO contents on crystallization and dielectric properties of PbO–SrO–Na2O–Nb2O5–SiO2 glass–ceramics system

PbO–SrO–Na₂O–Nb₂O₅–SiO₂ glass–ceramics were prepared via roll-quenching followed by controlled crystallization from 700 °C to 900 °C. The effects of PbO and SrO contents on crystallization and dielectric properties were investigated. The results show that Pb₂Nb₂O₇, Sr₂Nb₂O₇ and their solid solutions crystallize at 700 °C, NaNbO₃ is the primary phase at 800 °C, Pb₂Nb₂O₇ disappears and PbNb₂O₆ forms at 900 °C. The dielectric properties of the glass–ceramics formed through controlled crystallization has a strong dependence on the phase compositions that were developed during heat treatment. The highest dielectric constants (∼600) are found in samples with 6.0 mol% SrO annealed at 900 °C for 3 h. The dielectric–temperature characteristics of the samples show stability over the range from −60 °C to 180 °C, except the sample without SrO heated at 900 °C.     

Effect of different nucleation catalysts on the crystallization of Li2O–ZnO–MgO–Al2O3–SiO2 glasses

Based on local raw materials, a range of LiZnMg aluminosilicate glasses were prepared to investigate the influence of TiO₂, Cr₂O_3, and ZrO₂ on the crystallization behaviour and thermal expansion characteristics. Differential thermal analysis showed that the crystallization propensity increases in the order TiO₂ > Cr₂O₃ > ZrO₂. Virgilite, β-spodumene ss, gahnite, enstatite and cristobalite were formed in the prepared glass-ceramics. The microstructure of glass-ceramic samples showed growths of rounded and subrounded grains in the base sample, whereas, somewhat rod-like and accumulated growths appeared in samples containing ZrO₂. However, a rather homogeneous texture of accumulated growths was developed in glass-ceramics containing TiO₂ and Cr₂O₃. The coefficient of thermal expansion of parent glasses was sensitive to the type of nucleating agent added (Cr₂O₃ > TiO₂ > ZrO₂) varying from 24.8 × 10⁻⁷ to 65.1 × 10⁻⁷ °C⁻¹ being almost unchanged with the heat-treatment. The microhardness values of glass-ceramic samples were in the 763–779 kg/mm² range.     

合成气直接制低碳烯烃用Fe/K/Mg–O–Al催化剂

传统费托合成着眼于制取蜡/油等长碳链饱和烃,其催化剂的"金属/酸性氧化物"界面可以极化和稳定反应中间体,从而促进加氢和C—C偶合,有助于较长链烷烃的生成。为了从合成气直接获取高附加值的低碳烯烃,催化剂设计理念应该与以制取较长链烷烃为目的的传统费托催化剂取法相异。该文着眼于"弱加氢金属/固体碱型载体"费托合成制低碳烯烃催化剂的基础研究,采用表面碱性的载体和碱性的钾助剂,逆转上述传统催化剂中"金属/酸性氧化物"之间界面的状况,削弱对加氢和C—C偶合的促进,达到抑制加氢、抑制C—C偶合的目的。所测Fe/K/Mg-O-Al系列催化剂的烯烷比取决于强碱性位的数量及其占总碱性位的比值。在1200℃钝化处理条件下,与简单MgO担载的弱碱性催化剂相比,复合氧化物MgAl_2O_4担载的强碱性催化剂将低碳烯烃(C_2=～C_4=)产物分布值显著提高了84%,将C_2～C_4烯烷比显著提高了266%。     

Multiferroic ceramics in BaO–Y2O3–Fe2O3–Nb2O5 system

Multiferroic ceramics in BaO–Y₂O₃–Fe₂O₃–Nb₂O₅ system were synthesized and their dielectric, ferroelectric and magnetic properties were evaluated. XRD results showed that the ceramic composite consists of a major phase of tetragonal tungsten bronze structured Ba₂YFeNb₄O₁₅, and minor phases of monoclinic YNbO₄ and hexagonal Ba₃Fe₂Nb₆O₂₁. Three dielectric relaxations were observed in the temperature range from 125 to 575 K. The relaxor dielectric behavior in the temperature range from 125 to 350 K was attributed to the random occupation of Fe³⁺ and Nb⁵⁺ ions at B site of the tungsten bronze structure. The electrode polarization and the inhomogeneous structure contributed to the high-temperature and middle-temperature dielectric relaxations, respectively. Both the ferroelectric hysteresis loop and the magnetic hysteresis loop were measured, which suggested that the synthesized ceramic composite was a promising candidate of multiferroics.     

基于UiO–66–NH2@Eu–MOFs比率荧光探针的构建及其对PO43–检测

以发射蓝色荧光的Ui O–66–NH₂和发射红色荧光的Eu–MOFs为荧光基团，构建了比率荧光探针(Ui O–66–NH₂@Eu–MOFs)，成功应用于环境水样中的微量PO₄^3–的检测。将发射蓝色荧光UiO–66–NH₂与发射红色荧光Eu–MOF结合，构建了测定环境水样中的微量PO₄^3–的比率荧光探针。结果表明：当PO₄^3–存在时，由于配体–金属电荷转移(LMCT)效应的减弱，导致UiO–66–NH₂的荧光增强；另一方面，PO₄^3–和Eu³⁺的强配位作用将阻止配体–金属的能量转移(LMET)，破坏了“天线”效应并导致Eu–MOF的荧光猝灭，在最优条件下，F₄₄₅/F₆₃₃与PO₄^3–在1～12μmol/L浓度范围内呈现...     

Densification and microwave dielectric properties of CaO–B2O3–SiO2 system glass–ceramics

In order to relieve the narrow processing window and poor material compatibility in practical applications as well as understand the microwave dielectric properties, investigation on the formulations of CaO/B₂O₃/SiO₂ glasses on their structure, thermal properties, and microwave properties were performed in this study. Six glasses with different molar ratios of CaO/B₂O₃/SiO₂ (designed as CBS-3, CBS-5, CBS-7, CBS-8, CBS-9, and CBS-10) were prepared and pulverized. Results indicate that most softening points of glasses are ranging from 680 to 710 °C. They were sintered at different temperatures to reach maximum densification. Among various glass formulations, CBS-9 glass–ceramic containing the largest amount of SiO₂ has the lowest CTE. The dielectric constants can be divided into two groups including around 4–5 and 7–8, and the dielectric losses (tan δ) are all below 0.005 in the frequency of ≈10 GHz. The dielectric constants and dielectric losses are generally frequency dependent. For CBS-9 glass–ceramic, the dielectric constant and dielectric loss at 4.7 and 18.6 GHz are 4.13 and 0.0018, and 4.20 and 0.0063, respectively.     

PE–HD/PE–LD振动挤出预测模型及其应用

基于BP人工神经网络,研究高密度聚乙烯(PE–HD)、低密度聚乙烯(PE–LD)材料的振动挤出加工过程,建立螺杆转速、振动及口模诸因子与挤出胀大、压力和功率等输出特性参数间精确、高效、简洁的非线性映射关系,为挤出加工参数的优化和挤出加工质量的控制提供依据。结果证明,基于BP神经网络模型能够很好地预测聚合物挤出加工特性参数,所建网络具有精确、高速、自适应等特点。     

钛合金熔炼用Y2O3–Al2O3–MgO–CaO系耐火材料的设计与制备

坩埚耐火材料对钛合金熔炼的质量非常重要,为开发高性能新型坩埚材料,以工业Y₂O₃和Al₂O₃–MgO–CaO系粉末(AMC)为原料,制备出Y₂O₃–Al₂O₃–MgO–CaO系复合耐火材料,研究了烧结温度(1 500℃、1 600℃)和AMC含量(0、25%、50%、75%和100%,质量分数)对所制备耐火材料的物相组成、烧结性能(线收缩率、体积收缩率、显气孔率、体积密度)、常温耐压强度、抗热震性能和显微结构的影响。结果表明：相对于Y₂O₃和AMC材料,复合材料的性能均有所提高;提高烧结温度,其性能更佳;且随着AMC含量的提高,复合材料的线收缩率、体积收缩率、体积密度和常温耐压强度随之增大,显气孔率降低;当AMC的质量含量为75%时,1 500℃烧结3 h制得复合材料的综合性能最优,其显气孔率为4.37%,常温耐压强度为274.99 MPa,3次水冷热震后残余强度为16...     

Controlled partial oxidation of methane to methanol/formaldehyde over Mo–V–Cr–Bi–Si oxide catalysts

The non-catalytic and catalytic oxidations of CH₄ over Mo–V–Cr–Bi–Si oxide catalysts were investigated in a tubular reactor and the catalysts were characterized by XRD, XPS and TPR. Contents of Bi in the catalysts influenced the combination of Mo–V–Bi–O species and, consequently, influenced the TPR reduction temperature of the catalysts. The catalysts exhibited more selective production of methanol when the TPR reduction peaks shifted to lower temperature.